The objectives of this study were to undertake a clonal analysis of cellular immune response mediated by cytotoxic T cells (CTL) and by natural killer (NK) cells in an autologous human melanoma system and to examine the cellular and molecular basis of cytotoxic unresponsiveness against autologous melanoma cells. To test the hypothesis that cytotoxic unresponsiveness against autologous melanoma cells may result from antigen-specific suppression, we planned to clone autoreactive CTL after in vitro autologous-mixed lymphocyte-tumor cell interaction (MLTI) and then use the clones in cytotoxicity assays to search for putative cellular and/or humoral suppression factor. Using several autologous melanoma systems, including a melanoma line (VIP) and an autologous in vitro-transformed fibroblast line (VIP-F:T), several major goals have been accomplished. (1)\In the VIP system we demonstrated that CTL clones expressing cytotoxicity restricted to autologous melanoma cells can be generated. The cytotoxicity of the CTL clone, however, could not be modulated with autologous serum or with blood lymphocytes. (2)\We were able to establish functional human-mouse CTL hybrids that appeared to express the cytotoxic specificity of the hybridized CTL. (3)\Using the in vitro-transformed fibroblast system, we demonstrated the operational existence of autologous NK cells activities that express target receptor specificity and protect nude mice from tumorigenic challenge of the transformed cells. (4)\Multiple colonies and clones generated in other systems are under analysis. Finally, in one of our autologous systems, we have clearly identified the existence of both suppressor and inducer cells (isolated from tumor-affected lymph nodes) that are capable of suppressing the generation of cytotoxic immune response in MLTI against the autologous melanoma cells. (IS)